1. Field of the Invention
The present invention relates to a solid-state image pickup device that can improve the photoelectric conversion efficiency of a unit pixel and a method for producing the same.
2. Description of the Related Art
A complementary metal oxide semiconductor (CMOS) type solid-state image pickup device, which is one type of image sensor, includes a pixel area and peripheral circuits that drive the pixel area and process signals. Miniaturization technologies for the peripheral circuits have been generally applied to the pixel area. In addition, in the element-isolation of a pixel of the recent fine CMOS type solid-state image pickup device, a method of shallow trench isolation (STI) has been used as in the case of the peripheral circuits.
FIG. 7 is a cross-sectional view showing a schematic structure of a known general CMOS image sensor.
In FIG. 7, the CMOS image sensor includes an n-type silicon semiconductor substrate 1; a p-type semiconductor well region 2 disposed on the n-type silicon semiconductor substrate 1; a p+-type hole accumulation layer 3, an n-type signal charge accumulation region 4, a reading region 11, an n+-type reading part (FD) 12, and a trench 5 for shallow trench isolation (STI), which are disposed in the p-type semiconductor well region 2. An insulating material 6 such as silicon oxide is embedded in the trench 5 and a P+-type STI side wall layer 7 is disposed outside of the insulating material 6. A reading gate 9 is disposed above the reading region 11 with an insulating film 8 disposed therebetween. A reset gate 10 is disposed adjacent to the reading gate 9. A light-receiving part of such a CMOS image sensor is composed of an embedded photodiode including the hole accumulation layer 3 provided on the top face of the substrate and the signal charge accumulation region 4 provided under the hole accumulation layer 3 (refer to Japanese Unexamined Patent Application Publication No. 2002-231929).